Investigating Boat Noise in Wellfleet Harbor, MA

Sound plays an important role in marine environments, but growing anthropogenic noise levels in the oceans threaten marine animals’ ability to utilize essential sound signals. Anthropogenic noise pollution from military sonar, seismic airgun arrays, and shipping traffic can harm cetaceans in three ways: by causing physical injury to the animal, by masking biological important sounds in the environment, and by provoking behavioral changes. My research was part of a larger project, which aims to establish a Passive acoustic monitoring (PAM) system to detect cetacean vocalizations within and around Wellfleet Harbor in addition to possible acoustic disturbances from vessel noise. The broader study, part of research conducted by Dr. Laela Sayigh at WHOI, will attempt to determine if the vocalizations recorded can be utilized to predict mass stranding events and aid in the mitigation of such events. For my project, I analyzed underwater recordings from the harbor to determine presence of boat noise and ascertain the potential for masking. I made underwater recordings in Wellfleet Harbor, MA from 22 April, 2014 to 23 July, 2014. I analyzed the files to determine boat noise occurrence and characteristics. Overall, boat noise occurred in 32% of all recordings. I concluded that boat presence occurred frequency in Wellfleet Harbor, MA (~1/3 of the time). Boat noise occurrences followed expected day/night cycle patterns, but not expected tidal cycle patterns. Boat noise characteristics varied with deployment period, day/night cycle, and tidal cycle the observed patterns are unlikely to impact the current WHOI project. Boise noise frequency parameters, however, show some overlap with anecdotal dolphin vocalizations and could present problems for detection. I advised project managers at WHOI to adopt a precautionary approach when taking the next steps in the project, and made the following recommendations: WHOI should create boat noise filters for their detectors, conduct longer-term studies of boat noise in the harbor, pair the acoustic data with visual surveys of boats, and explore dolphin behavior in response to boat presence and noise utilizing a combination of acoustics and visual methods.